The present invention relates to a liquid toner composition adapted for use in, particularly, an electrophotography, an electrostatic printing and an information recording.
The conventional liquid toner composition adapted for an electrophotography comprises in general an electrically insulating liquid material, coloring particles having a particle diameter of 0.1 to 1 .mu.m and dispersed in the liquid material, and a resin soluble in the electrically insulating material and serving to disperse, fix and adjust the electrical charge of the coloring particles. Such a liquid toner is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-134468.
The coloring particles contained in the liquid toner composition of this type have a small particle diameter, leading to an excellent resolution. In addition, the composition can be prepared relatively easily. On the other hand, the toner composition is poor in its fixing properties. If the composition is used over a long period of time while replenishing toner of a higher concentration, the image quality is rendered defective by the change in the concentration of the resin dissolved in the electrically insulating material.
To overcome the above-noted difficulty, proposed is a liquid toner composition prepared by dispersing particles, including colorant particles in some cases, of resin in an electrically insulating material, said resin being insoluble at room temperature in said electrically insulating liquid material. However, if the resin particles are prepared by polymerization, the reaction is restricted by various polymerizing conditions. In addition, in order to obtain a satisfactory liquid toner composition, it is necessary in some cases to remove the initiator, unreacted monomers, etc. attached to the surfaces of the resin particles after the polymerization. Further, where resin is once dissolved in a solvent under heat, followed by cooling the resultant solution to cause precipitation of resin particles, it is difficult to control as desired the particle diameter of the resin particles.
Under the circumstances, the present inventors previously developed an effective method and already filed a patent application for the particular method. In this method, an olefin resin is dissolved under heat in a solvent having a high temperature dependency in its capability of dissolving the resin and having its solubility parameter, hereinafter referred to as SP, adjusted to control as desired the diameter of the resin particles, followed by lowering the solubility of the resin in the resultant solution so as to obtain resin particles having a desired average particle diameter and a narrow range of the particle size distribution. Further, the present inventors have now developed a liquid toner composition containing the above-noted resin particles and adapted for producing a high quality image and also developed a method of manufacturing the composition, leading to the present invention.